Israeli Prime Minister Benjamin Netanyahu said on Tuesday an airstrike that killed seven people working for celebrity chef Jose Andres' World Central Kitchen (WCK) charity in Gaza was unintended and "tragic", and the military pledged an independent inquiry.

The Israeli military confirmed the deadly strike on a WCK convoy that killed citizens from Australia, Britain and Poland as well as Palestinians and a dual citizen of the United States and Canada.

WCK said they were travelling in two armoured cars emblazoned with the charity's logo and another vehicle.

The military expressed "sincere sorrow" and promised an independent investigation into the incident, which drew widespread condemnation and ratcheted up pressure for steps to ease the disastrous humanitarian situation in Gaza.

"Unfortunately in the past day there was a tragic event in which our forces unintentionally harmed non-combatants in the Gaza Strip," Netanyahu said in a video statement.

"This happens in war. We are conducting a thorough inquiry and are in contact with the governments. We will do everything to prevent a recurrence."

Israel has long denied accusations that it is hindering the distribution of urgently needed food aid in Gaza, which it has besieged in a war since October, saying the problem is caused by international aid groups' inability to get it to those in need.

Despite coordinating movements with the Israeli military, the convoy was hit as it was leaving its Deir al-Balah warehouse after unloading more than 100 tons of humanitarian food aid brought to Gaza by sea, WCK said.

"This is not only an attack against WCK, this is an attack on humanitarian organisations showing up in the most dire of situations where food is being used as a weapon of war," said Erin Gore, chief executive of WCK.

"This is unforgivable."

The Israeli military said it was conducting a thorough review at the highest levels to understand the circumstances of what it called a tragic incident, and pledged an investigation by "an independent, professional and expert body".

Israel has been under rising international pressure to alleviate the severe hunger in Gaza, which has been devastated by months of fighting the Palestinian Islamist group Hamas. Much of the densely populated territory has been laid waste and most of its 2.3 million population displaced.

Andres, who started WCK in 2010 by sending cooks and food to Haiti after an earthquake, said he was heartbroken and grieving for the families and friends of those who died in the airstrike.

"The Israeli government needs to stop this indiscriminate killing. It needs to stop restricting humanitarian aid, stop killing civilians and aid workers, and stop using food as a weapon."

WCK, which said last month it had served more than 42 million meals in Gaza over 175 days, announced it was pausing its operations in the region immediately and would make decisions soon about the future of its work.

Britain, Australia and Poland, countries which have generally been friendly towards Israel, all demanded action to protect aid workers, underlining Netanyahu's increasing diplomatic isolation over the situation in Gaza.

Australian Prime Minister Anthony Albanese confirmed the death of 44-year-old aid worker Lalzawmi "Zomi" Frankcom and said his government had contacted Israel to demand those responsible be held accountable.

Poland, which also lost a citizen, objected to the "disregard for international humanitarian law and the protection of civilians, including humanitarian workers."

China also condemned the killing of aid workers in Gaza.

Foreign Ministry spokesman Wang Wenbin said civilians should never be the target of attacks, and that Beijing supports an immediate ceasefire in Gaza.

Video obtained by Reuters showed a large hole in the roof of a four-wheel-drive WCK vehicle and its burned and torn interior, as well as paramedics moving bodies into a hospital and displaying the passports of three of those killed. (Reuters, additional reporting by RTHK)